Guided weapons make use of sensors and guidance algorithms to guide them, once launched, towards a designated target. Occasionally, it may be possible for target designation to occur automatically (for example, the designation of an aircraft silhouetted against a clear sky), but in many cases it will be necessary for an operator to designate the target to the weapon. Currently this is done by means of a targeting reticule. In some cases the reticule may be fixed to the launcher, such that the crosshairs are permanently fixed to the boresight of the weapon. Target designation is then achieved by moving the launcher until the crosshairs are over the target. In other cases a moving reticule is provided, so that the operator can move the reticule by means of a hand control, such as a joystick, using the whole hand, or sticks or D-pads, for which only the operator's thumbs are required.
However, both fixed and moveable reticule systems suffer from problems in target designation. In the case of handheld systems, using fixed reticules, particularly where the weapon and launch system is heavy, selection of a small target in a relatively large and cluttered field of view can be difficult, because the whole system must be moved in order to set the target. This makes fine movements, which may be difficult where the target is relatively small within the field of view, difficult. In contrast, the provision of a moving reticule can assist in such fine movements. However, for the operator to perform fine control movements of the reticule using thumbs, whilst using both hands to hold and steady a guided weapon system (weighing potentially tens of kilograms) can be difficult, and may be impossible where the operator is on a moving and unsteady platform. Similar problems exist for other weapon systems used when the operator is required to hold other equipment steady whilst designating a target; or where the operator is moving across ground on foot whilst attempting to designate a target.